Numerical simulation on tectonic thermal evolution at 8km in the Bozhong Depression considering sediment compression effects

The Bohai Sea, one of China’s four marginal seas, is also the country’s most resource-rich area in terms of offshore oil and gas reserves. The central Bohai Bay Depression (Bohai Central Depression) has a maximum sedimentary thickness of up to 7-8 km, and a distinct geothermal anomaly is observed at the depression’s center. During the formation of the Bohai Central Depression, the compression of sediments induces a series of physical changes and thermal effects. These effects not only influence the tectonic thermal evolution during sedimentation but also affect the oil and gas reservoir formation in the sedimentary strata. In this study, a theoretical model considering sediment compression effects was developed using COMSOL, to simulate the sediment compression process and the geothermal structure and thermal evolution history in the central depression of the Bohai Sea. The results indicate a strong correlation between the sediment compression effect in the Bohai Central Depression and the underlying geothermal anomalies. Sediment compression alters the porosity of the reservoir, leading to changes in the geothermal structure and thermal evolution characteristics of the reservoir. The compression of sediments impedes heat transfer within the reservoir, increasing the basal temperature and reducing the overall geothermal gradient. Our thermal modeling results provide significant scientific insights into understanding the thermal effects of sediment compression in the Bohai Central Depression and its implications for oil and gas accumulation.